Components and catalysts for the polymerization of olefins

ABSTRACT

The present invention relates to components of catalysts for the polymerization of olefins comprising a metallocene compound and a magnesium halide which have particular values of porosity and surface area. In particular the components of the invention have surface area (BET) greater than about 50 m 2  /g, porosity (BET) greater than about 0.15 cm 3  /g and porosity (Hg) greater than 0.3 cm 3  /g, with the proviso that when the surface area is less than about 150 m 2  /g, the porosity (Hg) is less than about 1.5 cm 3  /g. The components of the invention are particularly suitable for the preparation of catalysts for the gas-phase polymerization of α-olefins.

The present invention relates to components of catalysts for thepolymerization of olefins, the catalysts obtained therefrom and the useof said catalysts in the polymerization of olefins CH₂ ═CHR, in which Ris hydrogen or an alkyl, cycloalkyl or aryl radical with 1-10 carbonatoms. Another aspect of the present invention relates to the polymersobtained using said catalysts.

Catalysts are known from the literature that are obtained from compoundsML_(x) in which M is a transition metal, especially Ti, Zr and Hf, L isa ligand coordinating on the metal, x is the valence of the metal and atleast one of the ligands L has cyclo-alkadienyl structure. Catalysts ofthis type using compounds Cp₂ TiCl₂ or Cp₂ ZrCl₂ (Cp=cyclopentadienyl)are described in U.S. Pat Nos. 2,827,446 and 2,924,593. The compoundsare used together with alkyl-Al compounds in the polymerization ofethylene. The catalytic activity is very low. Catalysts with very highactivity are obtained from compounds Cp₂ ZrCl₂ or Cp₂ TiCl₂ and fromtheir derivatives substituted in the cyclopentadienyl ring, in which theCp ring can also be condensed with other rings, and from polyalumoxanecompounds containing the repeating unit -(R)AlO--, in which R is a loweralkyl, preferably methyl (U.S. Pat No. 4,542,199 and EP-A-129368).

Catalysts of the type mentioned above, in which the metallocene compoundcontains two indenyl or tetrahydroindenyl rings bridge-bonded throughlower alkylenes or through other divalent radicals, are suitable for thepreparation of stereoregular polymers of propylene and other α-olefins(EP-A-185918).

Stereospecific catalysts are also obtained from dicyclopentadienylcompounds in which the two rings are substituted differently with groupshaving steric hindrance such as to prevent rotation of the rings aboutthe axis of coordination with the metal.

Substitution of indenyl or tetrahydroindenyl in suitable positions givescatalysts that have very high stereospecificity (EP-A-485823,EP-A-485820, EP-A-519237, U.S. Pat. No. 5,132,262 and U.S. Pat. No.5,162,278).

The metallocene catalysts described above produce polymers with a verynarrow molecular weight distribution (Mw/Mn of about 2).

Some of these catalysts also have the property of forming copolymers ofethylene with α-olefins of the LLDPE type or ethylene/propyleneelastomeric copolymers with very uniform distribution of the comonomerunits. The LLDPE polyethylene obtained is further characterized by lowsolubility in solvents such as xylene or n-decane.

The polypropylene obtained with the highly stereospecific catalystsmentioned above has greater crystallinity and a higher deformationtemperature compared with the polymer that can be obtained with theconventional Ziegler-Natta catalysts.

However, these metallocene catalysts have a considerable drawback withrespect to the possibility of being employed in industrial processes forproduction of polyolefins that are not carried out in solution, owing tothe fact that they are soluble in the reaction medium in which they areprepared and in the liquid medium of polymerization.

In order to be usable in gas-phase polymerization processes, thecatalysts must be supported on suitable supports which endow the polymerwith appropriate morphological properties.

Supports of various kinds have been used, including, among others,porous metal oxides such as silica or porous polymeric supports such aspolyethylene, polypropylene and polystyrene. The halides of magnesiumare also used as supports. In some cases magnesium halides are also usedas counterion of an ion pair in which the metallocene compound suppliesthe cation and a compound, such as a Mg halide, supplies the anion.

When Mg halide is used for supplying the anion, the catalytic system isformed by the halide present in solid form and the metallocene compounddissolved in a solvent. A system of this type cannot be used ingas-phase polymerization processes. Mg halide is preferably used infinely divided form that can be obtained by grinding.

As support, Mg halide is used in pulverized form, obtainable bygrinding. Catalysts obtained in this way are not of high performance.Sufficiently high yields can only be obtained when the Mg halide is usedin a form in which it is partially complexed with an electron-donorcompound, obtained by a special method of preparation.

Japanese Application. No. 168408/88 (published on Dec. 7, 1988)describes the use of magnesium chloride as support for metallocenecompounds, such as Cp₂ TiCl₂, Cp₂ ZrCl₂, Cp₂ Ti(CH₃)₂ for forming, withtrialkyl aluminium and/or polymethylalumoxane (MAO), catalysts for thepolymerization of ethylene. The component containing the magnesiumchloride is prepared by grinding MgCl₂ with the metallocene compound,also working in the presence of electron-donor compounds. Alternatively,the component is prepared by treating the metallocene with a liquidMgCl₂ -alcohol adduct and subsequent reaction with AlEt₂ Cl. Thecatalyst activity, referred to MgCl₂ is very low.

Catalysts comprising a metallocene compound of the type Cp₂ ZrCl₂supported on MgCl₂ in spherical form and partially complexed with anelectron-donor compound are described in U.S. Pat. No. 5,106,804. Theperformance of these catalysts is better than that described in JapaneseApplication No. 168408/88 but is still not satisfactory, since it is notpossible to obtain polymers containing sufficiently low residues of thecatalyst. The electron donor used must be free from atoms of activehydrogen and in addition must be uniformly distributed in the bulk ofthe Mg halide. Suitable supports cannot be obtained by mere mixing ofthe components. Homogeneous dispersion of the electron donor is obtainedby forming the Mg halide (by halogenation of Mg-dialkyls) in thepresence of a solvent containing the electron donor in dissolved form.The surface area of the Mg halide is not greater than 100 m² /g, and ispreferably between 30 and 60 m² /g. No information is given with respectto the porosity of the support. The electron-donor compound is used in aquantity of from 0.5 to 15 mol % based on the Mg halide; its presence isnecessary. The catalysts obtained have performance that is much lowerthan that of the corresponding unsupported catalysts in which themetallocene compound is used in solution.

Application EP-A-318048 describes catalysts in which a solid componentcomprising a compound of Ti supported on a magnesium chloride that hasparticular characteristics of surface area and of porosity and possiblyan electron-donor compound, is used with benzyl compounds of Ti or Zr orwith metallocene compounds of the type Cp₂ Ti(CH₃)₂ andbis-(indenyl)-Zr(CH₃)₂ for forming catalysts for polymerization ofethylene and of propylene. The weight ratio of metallocene to magnesiumchloride is very high (greater than 1), so it is necessary to remove themetallocene from the obtained polymer. The catalysts are used inprocesses that are carried out in the presence of a liquidpolymerization medium.

Application EP-A-4399164 describes bimetallic catalysts suitable for thepreparation of ethylene polymers with broad molecular weightdistribution (Mw/Mn between 4 and 14) obtained by supporting ametallocene on a solid component containing a Ti compound supported onMgCl₂. MAO or its mixtures with alkyl-Al are used as cocatalyst.Trialkyl-Al compounds are also used as cocatalysts but the catalyticactivity is low. The yields of these mixed catalysts with active centresderived either from the Ti compound supported on MgCl₂ or from themetallocene compound are very high when the catalysts are used in ahydrocarbon medium; on the other hand they are low when polymerizationis effected in the gas phase. This is probably due to the fact that,when using a hydrocarbon medium, as the metallocene compound is notfixed to the support in a stable form, it dissolves in the hydrocarbonpolymerization solvent. In practice, the obtained catalyst correspondsto a homogeneous catalyst in which the metallocene compound is used insolution. Working in the gas phase, the metallocene compound is presentas a solid and the catalyst obtained therefrom has an activity lowerthan that of the corresponding catalyst used in solution.

Application EP-A-522281 describes catalysts obtained from Cp₂ ZrCl₂supported on MgCl₂ and from mixtures of trialkyl-Al and compoundssupplying stable anions of the typedimethylaniline-tetrakis-(pentafluorophenyl)-borate. The catalysts areprepared by grinding the components and are used to polymerize ethylenein the presence of a solvent (toluene) with good yields (based onMgCl₂). In this case too, the metallocene compound is present largely insolution and not fixed to MgCl₂ and the relatively high activity basedon MgCl₂ is due essentially to the catalyst dissolved in thepolymerization medium.

Application EP-A-509944 describes catalysts usinganiline-tetrakis-(pentafluorophenyl)-borate or Lewis acids such as MgCl₂together with metallocene halides pre-reacted with alkyl-Al Compounds.The magnesium chloride is ground before being contacted with thepre-reacted metallocene compound. The yields of polymer based on the Mghalide are not high (less than about 100 g polymer/g MgCl₂). The Mghalide has surface are between 1 and 300 m² /g, preferably between 30and 300 m^(2/) g. Mg chloride with area between 30 and 300 m^(2/) g isobtained essentially by grinding the commercial chloride. In this caseit is difficult for the area to exceed 100-150 m^(2/) g and theporosities are relatively low (less than 0.1 cm³ /g). Also in the caseof the catalysts described in Application EP-A-509944 the yields shouldlargely be attributed to the metallocene compound dissolved in thepolymerization solvent.

Application EP-A-588404 describes catalysts obtained from metallocenecompounds supported on Mg halides prepared by halogenation of dialkyl-Mgor alkyl-Mg halides with SiCl₄ or SnCl₄. The yields of polymer(polyethylene) per g of solid component and per g of Zr are relativelyhigh, especially when the catalyst is obtained from MgCl₂ prepared usingSnCl₄. Again in this case it is to be assumed that the high catalyticactivity is due more to the catalyst derived from the metallocenecompound that dissolves in the polymerization medium than from thatderived from the metallocene compound actually supported on the Mghalide.

European Application EP-A-576213 describes catalysts obtained from asolution of MgCl₂ in an alkanol, from a trialkyl-Al compound and from ametallocene compound. The yields of polymer are very low. The catalystis practically inactive when the MgCl₂ solution is replaced by solidMgCl₂ activated by prolonged grinding.

Solid components have now unexpectedly been found that comprise ametallocene compound and a magnesium halide, capable of giving catalyststhat have very high activity in the polymerization of olefins,characterized by surface area (BET method) greater than about 50 m² /g,porosity (BET method) greater than about 0.15 cm³ /g and porosity (Hgmethod) greater/than 0.3 cm³ /g, with the proviso that when the surfacearea is less than about 150 m² /g, the porosity (Hg) is less than about1.5 cm³ /g.

The porosity and surface area according to the BET method are determinedusing the "SORPTOMATIC 1800" apparatus from Carlo Erba.

The porosity according to the Hg method is determined using a"Porosimeter 2000 series" porosimeter from Carlo Erba, following theprocedure described below.

The porosity (BET) is preferably above 0.2 cm³ /g and in particularbetween 0.3 and 1 cm³ /g. The surface area (BET) is preferably greaterthan 100 m² /g and more preferably greater than 150m² /g. A veryconvenient range is between 150 and 800 m² /g. Components with surfacearea less than 150 m² /g give catalysts with performance that is ofinterest, provided that the porosity (Hg method) is less than about 1.5cm³ /g, preferably between 0.4 and 1.2 cm³ /g, and in particular between0.5 and 1.1 cm³ /g.

The components are preferably used in the form of spherical particlessmaller than 150 μm.

In the components with surface area (BET) less than 150 m² /g more than50% of the porosity (BET) is due to pores with radius greater than 300 Åand preferably between 600 and 1000 Å.

The components with surface area (BET) greater than 150 m² /g and inparticular greater than 200 m² /g exhibit, along with porosity (BET) dueto pores with radius between 300 and 1000 Å, also porosity (BET) due topores with radius between about 10 and 100 Å. In general, more than 40%of the porosity (BET) is due to pores with radius greater than 300 Å.

The mean dimensions of the crystallites of Mg halide present in thesolid component are generally below 300 Å and more preferably below 100Å. The definition of the components of the invention also includes thosecomponents which, in normal conditions, do not display the values ofarea and porosity stated above but attain them after treatment with asolution of trialkyl-Al at 10% in n-hexane at 50° C. for 1 hour.

The components of the invention are prepared by supporting a metallocenecompound on an Mg halide or on a support containing Mg halide that hascharacteristics of surface area and of porosity that are within theranges stated for the catalytic component.

In general the surface area (BET) and the porosity (BET) and porosity(Hg) of the starting magnesium halide are greater than those of thecomponent obtained from it.

Preferred Mg halides have surface area (BET) greater than 200m² /g andmore preferably between 300 and 800m² /g and porosity (BET) greater than0.3 cm³ /g.

The Mg halide can comprise, in smaller proportions, other componentsacting as co-support or used for improving the properties of thecatalytic component. Examples of these components are AlCl₃, SnCl₄,Al(OEt)₃, MnCl₂, ZnCl₂, VCl₃, Si(OEt)₄.

The Mg halide can be complexed with electron-donor compounds notcontaining active hydrogen in a quantity up to about 30 mol %,preferably 5-15 mol % based on the Mg halide. Examples of electrondonors are ethers, esters, ketones.

The Mg halide can in its turn be supported on an inert support that hasarea and porosity such that the supported product has the values statedabove. Suitable inert supports can be metal oxides such as silica,alumina, silica-alumina, possessing porosity (BET) greater than 0.5 cm³/g and surface area (BET) greater than 200 m² /g and for example between300 and 600 m² /g.

Other inert supports can be porous polymers such as polyethylene,polypropylene and polystyrene.

Partially crosslinked polystyrene that has high values of surface areaand porosity is particularly suitable.

Polystyrenes of this type are described in U.S. Pat. No. 5,139,985,whose description of the method of preparation and supporting of themagnesium halide is included here for reference. These polystyrenesgenerally have surface area (BET) between 100 and 600 m² /g and porosity(BET) greater than 0.5 cm³ /g.

The amount of Mg halide that can be supported is generally between 1 and20% by weight based on the mixture. The preferred Mg halide is Mgchloride. The Mg halide can be supported according to known methods,starting from its solutions in solvents such as tetrahydrofuran or byimpregnation of the inert support with solutions of the halide in analcohol; the alcohol is then removed by reaction with a compound such asa trialkyl-Al or dialkyl-Al halide or silicon halides. The alcohols usedare generally alkanols with 1-8 carbon atoms.

A method that is very suitable for preparation of Mg halides that havethe characteristics of porosity and area stated above, consists ofreacting spherulized adducts of MgCl₂ with alcohols, the said adductscontaining from 0.1 to 3 mol of alcohol, with alkyl-Al compounds, inparticular triethyl-Al, triisobutyl-Al, AlEt₂ Cl.

A preparation of this type is described in U.S. Pat. No. 4,399,054 whosedescription is herein included for reference.

For the purpose of obtaining supports with morphological characteristicsthat are particularly suitable for gas-phase polymerization processes ina fluidized bed, the adduct of MgCl₂ with about 3 mol of alcohol shouldbe submitted, prior to reaction with the alkyl-Al, to a controlledpartial dealcoholizing treatment such as that described in EuropeanPatent Application EP-A-553806, to which reference is made for thedescription. The Mg halides thus obtained have a spheroidal shape, meandimensions less than 150 microns, surface area (BET) greater than 60-70m² /g and generally between 60 and 500 m² /g.

Other methods of preparation of the Mg halides suitable for preparationof the components of the invention are those described in EuropeanPatent Application EP-A-553805, whose description is herein included forreference.

Supporting of the metallocene compound is carried out according to knownmethods by bringing the Mg halide into contact, for example, with asolution of the metallocene compound, operating at temperatures betweenroom temperature and 120° C. The metallocene compound that is not fixedon the support is removed by filtration or similar methods or byevaporating the solvent.

The amount of metallocene compound supported is generally between 0.1and 5% by weight expressed as metal.

The atomic ratio of Mg to transition metal is generally between 10 and200; it can, however, be less and reach values of 1 or even less whenthe Mg halide is supported on an inert support.

The metallocene compounds are sparingly soluble in hydrocarbons (thehydrocarbon solvents most used are benzene, toluene, hexane, heptane andthe like). Their solubility increases considerably if the solventcontains a dissolved alkyl-Al compound such as triethyl-Al,triisobutyl-Al or a polyalkylalumoxane in particular MAO(polymethyl-alumoxane) in molar ratios with the metallocene compoundgreater than 2 and preferably between 5 and 100.

Impregnation of the support starting from the solution mentioned abovemakes it possible to obtain particularly active catalysts (the activityis greater than that of the catalysts that can be obtained fromsolutions of the metallocene compound that do not contain the alkyl-Alcompound or MAO).

The metallocene compounds that can be used are selected from thecompounds of a transition metal M selected from Ti, V, Zr and Hfcontaining at least one metal-π bond, and comprising preferably at leastone ligand L coordinated on the metal M possessing a mono- or polycyclicstructure containing conjugated π electrons.

The said compound of Ti, V, Zr or Hf is preferably selected fromcomponents possessing the structure:

    Cp.sup.I MR.sub.a.sup.1 R.sub.b.sup.2 R.sub.c.sup.3        (I)

    Cp.sup.I 1Cp.sup.II MR.sub.a.sup.1 R.sub.b.sup.2           (II)

    (Cp.sup.I -A.sub.e -Cp.sup.II)M.sup.1 R.sub.a.sup.1 R.sub.b.sup.2 (III)

in which M is Ti, V, Zr or Hf; Cp^(I) and Cp^(II), identical ordifferent, are cyclopentadienyl groups, including substituted ones; twoor more substituents on the said cyclopentadienyl groups can form one ormore rings possessing from 4 to 6 carbon atoms; R¹, R² and R³, identicalor different, are atoms of hydrogen, halogen, an alkyl or alkoxyl groupwith 1-20 carbon atoms, aryl, alkaryl or aralkyl with 6-20 carbon atoms,an acyloxy group with 1-20 carbon atoms, an allyl group, a substituentcontaining a silicon atom; A is an alkenyl bridge or one with structureselected from: ##STR1## ═BR₁, ═AlR₁, --Ge--, --Sn--, --O--, --S--,═SO,═SO₂, ═NR₁, ═PR₁, ═P(O)R₁, in which M₁ is Si, Ge, or Sn; R₁ and R₂,identical or different, are alkyl groups with 1-4 carbon atoms or arylgroups with 6-10 carbon atoms; a, b, c are, independently, integers from0 to 4; e is an integer from 1 to 6 and two or more of the radicals R¹,R² and R³ can form a ring. In the case when the Cp group is substituted,the substituent is preferably an alkyl group with 1-20 carbon atoms.

Representative compounds that have formula (I) include: (Me₅ Cp)MMe₃,(Me₅ Cp)M(OMe)₃, (Me₅ Cp)MCl₃, (Cp)MCl₃, (Cp)MMe₃, (MeCp)MMe₃, (Me₃Cp)MMe₃, (Me₄ Cp)MCl₃, (Ind)MBenz₃, (H₄ Ind)MBenz₃, (Cp)MBu₃.

Representative compounds that have formula (II) include: (Cp)₂ MMe₂,(Cp)₂ MPh₂, (Cp)₂ MEt₂, (Cp)₂ MCl₂, (Cp)₂ M(OMe)₂, (Cp)₂ M(OMe)Cl,(MeCp)₂ MCl₂, (Me₅ Cp)₂ MCl₂, (Me₅ Cp)₂ MMe₂, (Me₅ Cp)₂ MMeCl, (Cp)(Me₅Cp)MCl₂, (1-MeFlu)₂ MCl₂, (BuCp)₂ MCl₂, (Me₃ Cp)₂ MCl₂, (Me₄ Cp)₂ MCl₂,(Me₅ Cp)₂ M(OMe)₂, (Me₅ Cp)₂ M(C₆ H₅)₂, (Me₅ Cp)₂ M(CH₃)Cl, (EtMe₄ Cp)₂MCl₂, (C₆ H₅)Me₄ Cp!₂ MCl₂, (Et₅ Cp)₂ MCl₂, (Me₅ Cp)₂ M(C₆ H₅)Cl, (Ind)₂MCl₂, (Ind)₂ MMe₂, (H₄ Ind)₂ MCl₂, (H₄ Ind)₂ MMe₂, { Si(CH₃)₃ !Cp}₂MCl₂, { Si(CH₃)₃ !₂ Cp}₂ MCl₂, (Me₄ Cp)(Me₅ Cp)MCl₂.

Representative compounds of formula (III) include: C₂ H₄ (Ind)₂ MCl₂, C₂H₄ (Ind)₂ MMe₂, C₂ H₄ (H₄ Ind)₂ MCl₂, C₂ H₄ (H₄ Ind)₂ MMe₂, Me₂ Si(Me₄Cp)₂ MCl₂, Me₂ Si(Me₄ Cp)₂ MMe₂, Me₂ SiCp₂ MCl₂, Me₂ SiCp₂ MMe₂, Me₂Si(Me₄ Cp)₂ MMeOMe, Me₂ Si(Flu)₂ MCl₂, Me₂ Si(2-Et-5-iPrCp)₂ MCl₂, Me₂Si(H₄ Ind)₂ MCl₂, Me₂ Si(H₄ Flu)₂ MCl₂, Me₂ SiCH₂ (Ind)₂ MCl₂, Me₂Si(2-Me-H₄ Ind)₂ MCl₂, Me₂ Si(2-MeInd)₂ MCl₂, Me₂ Si(2-Et-5-iPr-Cp)₂MCl₂, Me₂ Si(2-Me-5-EtCp)₂ MCl₂, Me₂ Si(2-Me-5-Me-Cp)₂ MCl₂, Me₂Si(2Me-4,5-benzoindenyl)₂ MCl₂, Me₂ Si(4,5-benzoindenyl)₂ MCl₂, Me₂Si(2-EtInd)₂ MCl₂, Me₂ Si(2-iPr-Ind)₂ MCl₂, Me₂ Si(2-t-butyl-Ind)MCl₂,Me₂ Si(3-t-butyl-5-MeCp)₂ MCl₂, Me₂ Si(3-t-butyl-5-MeCp)₂ MMe₂, Me₂Si(2-MeInd)₂ MCl₂, C₂ H₄ (2-Me-4,5-benzoindenyl)₂ MCl₂, Me₂C(Flu)CpMCl₂, Ph₂ Si(Ind)₂ MCl₂, Ph(Me)Si(Ind)₂ MCl₂, C₂ H₄ (H₄Ind)M(NMe₂)OMe, isopropylidene-(3-t-butyl-Cp)(Flu)MCl₂, Me₂ C(Me₄Cp)(MeCp)MCl₂, MeSi(Ind)₂ MCl₂, Me₂ Si(Ind)₂ MMe₂, Me₂ Si(Me₄ Cp)₂MCl(OEt), C₂ H₄ (Ind)₂ M(NMe₂)₂, C₂ H₄ (Me₄ Cp)₂ MCl₂, C₂ Me₄ (Ind)₂MCl₂, Me₂ Si(3-Me-Ind)₂ MCl₂, C₂ H₄ (2-Me-Ind)₂ MCl₂, C₂ H₄ (3-Me-Ind)₂MCl₂, C₂ H₄ (4,7-Me₂ -Ind)₂ MCl₂, C₂ H₄ (5,6-Me₂ -Ind)₂ MCl₂, C₂ H₄(2,4,7-Me₃ Ind)₂ MCl₂, C₂ H₄ (3,4,7-Me₃ Ind)₂ MCl₂, C₂ H₄ (2-Me-H₄ Ind)₂MCl₂, C₂ H₄ (4,7-Me₂ -H₄ Ind)₂ MCl₂, C₂ H₄ (2,4,7-Me₃ -H₄ Ind)₂ MCl₂,Me₂ Si(4,7-Me₂ -Ind)₂ MCl₂, Me₂ Si(-5,6-Me₂ -Ind)₂ MCl₂, Me₂Si(2,4,7-Me₃ -H₄ Ind)₂ MCl₂.

In the simplified formulae given above, the symbols have the followingmeanings: Me=methyl, Et=ethyl, iPr=isopropyl, Bu=butyl, Ph=phenyl,Cp=cyclopentadienyl, Ind=indenyl, H₄ Ind=4,5,6,7-tetra-hydroindenyl,Flu=fluorenyl, Benz=benzyl, M=Ti, Zr or Hf, preferably Zr.

Also preferred are metallocene compounds having the formula (Me₅ Cp)₂M(OH)Cl or (Me₅ Cp)₂ M(OH)₂, wherein M is a transition metal selectedfrom Ti, V, Zr and Hf, Me=methyl and Cp=cyclopentadienyl.

Compounds of the type Me₂ Si(2-Me-Ind)₂ ZrCl₂ and Me₂ Si(2-Me-H₄Ind)ZrCl₂ and their methods of preparation are described respectively inEuropean Applications EP-A-485822 and 485820 whose description isincluded here for reference.

Compounds of the type Me₂ Si(3-t-butyl-5-MeCp)₂ ZrCl₂ and of the typeMe₂ Si(2-Me-4,5-benzoindenyl)ZrCl₂ and their method of preparation aredescribed respectively in U.S. Pat. No. 5,132,262 and in PatentApplication EP-A-549900 whose description is included here forreference.

The components of the invention form, with alkyl-Al compounds or withpolyalkyl-alumoxane compounds or their mixtures, catalysts that possessvery high activity relative to the Mg halide.

The alkyl-Al compound is generally selected from compounds of formulaAlR₃, in which R is an alkyl that has 1-12 carbon atoms, and thealumoxane compounds containing the repeating unit -(R⁴)AlO--, in whichR⁴ is an alkyl radical containing from 1 to 6 carbon atoms, and the saidalumoxane compounds contain from 2 to 50 repeating units that have theformula described above. Typical examples of compounds that have theformula AlR₃ are trimethyl-Al, triethyl-Al, triisobutyl-Al,tri-n-butyl-Al, trihexyl-Al, trioctyl-Al. Among the alumoxane compounds,use of MAO is preferable. Mixtures of alkyl-Al compounds, preferablytriisobutyl- Al, and alumoxane compounds, preferably MAO, are also usedadvantageously.

When the transition metal compound containing at least one M-π bond isof the type described in formulae (II) and (III), the compounds obtainedfrom the reaction between AlR₃ and H₂ O in molar ratios between 0.01 and0.5 can be used advantageously.

In general the alkyl-Al compound is used in molar ratios relative to thetransition metal between 10 and 5000, preferably between 100 and 4000,and more preferably between 500 and 2000.

The catalysts of the invention can be used for (co)polymerizing CH₂ ═CHRolefins, in which R is hydrogen or an alkyl radical with 1-10 carbonatoms or an aryl.

They are used in particular for polymerizing ethylene and its mixtureswith α-olefins of the type stated above in which R is an alkyl radical.

The catalysts, particularly those obtained from compounds of the type C₂H₄ (Ind)₂ ZrCl₂, C₂ H₄ (H₄ Ind)ZrCl₂ and Me₂ Si(Me₄ Cp)₂ ZrCl₂, aresuitable for producing LLDPE (copolymers of ethylene containing smallerproportions, generally below 20 mol %, of α-olefin C₃ -C₁₂)characterized by relatively low density values in relation to thecontent of α-olefin, with reduced solubility in xylene at roomtemperature (below approx. 10% by weight) and with molecular weightdistribution Mw/Mn between about 2.5 and 5.

The polypropylenes that can be obtained with the catalysts using achiral metallocene compound are characterized by increasedstereoregularity, high molecular weights that are easily controllable,and high degree of crystallinity.

The chiral metallocene compounds that can be used are for example of thetype described in European Application EP-A-485823, EP-A-485820,EP-A-519237, and U.S. Pat. Nos. 5,132,262, and 5,162,278.

The following examples are given for the purpose of illustrating but notlimiting the invention. The properties stated are determined inaccordance with the following methods:

Porosity and surface area (BET): are determined according to BET methods(apparatus used: SORPTOMATIC 1800 from Carlo Erba). The porosity iscalculated from the integral pore distribution curve in function of thepores themselves.

Porosity and surface area with mercury: are determined by immersing aknown quantity of the sample in a known quantity of mercury inside adilatometer and then gradually increasing the pressure of the mercuryhydraulically. The pressure of introduction of the mercury into thepores is a function of their diameter. Measurement is effected using a"Porosimeter 2000 series" porosimeter from Carlo Erba. The porosity,pore distribution and surface area are calculated from data on thedecrease, of volume of the mercury and from the values of the appliedpressure.

The porosity and surface areas stated in the descriptions and in theexamples are referred to pore dimensions up to 10000 Å.

Size of the catalyst particles: is determined by a method based on theprinciple of optical diffraction of monochromatic laser light with the"Malvern Instr. 2600" apparatus. The average size is stated as P50.

Melt Index E (MIE): determined according to ASTM-D 1238, method E.

Melt Index F (MIF): determined according to ASTM-D 1238, method F.

Ratio of degrees (F/E): ratio between Melt Index F and Melt Index E.

Flowability: is the time taken for 100 g of polymer to flow through afunnel whose discharge hole has a diameter of 1.25 cm and whose wallsare inclined at 20° to the vertical.

Apparent density: DIN 53194.

Morphology and granulometric distribution of the particles of polymer:ASTM-D 1921-63.

Fraction soluble in xylene: measured by dissolving the polymer inboiling xylene and determining the insoluble residue after cooling to25° C.

Content of comonomer: percentage by weight of comonomer determined fromIR spectrum.

Density: ASTM-D 792.

Average size of MgCl₂ crystallites D(110)!: is determined frommeasurement of the width at half-height of the (110) diffraction linethat appears in the X-ray spectrum of the magnesium halide, applyingScherrer's equation:

    D(110)=(K·1.542·57.3)/(B-b)cos θ,

in which:

K=constant (1.83 in the case of magnesium chloride);

B=half-width (in degrees) of the (110) diffraction line;

b=instrumental broadening;

θ=Bragg angle.

In the case of magnesium chloride, the (110) diffraction line appears atan angle 2θ of 50.2°.

EXAMPLES EXAMPLE 1

Preparation of the support

A spherical adduct MgCl₂.3EtOH was prepared according to the proceduredescribed in Example 2 of Patent U.S. Pat. No. 4,399,054, operating at3000 rpm instead of at 10000 rpm. The adduct was partially dealcoholizedby heating in a stream of nitrogen at temperatures increasing from 30°C. to 180° C., until an adduct containing 10% by weight of EtOH wasobtained.

Preparation of the metallocene/triisobutylaluminium solution

A reactor with capacity of 1000 cm³, equipped with an anchor stirrer andtreated with N₂, was fed with 382.5 cm³ of triisobutylaluminium (TIBAL)in hexane solution (100 g/liter) and 14.25 g of ethylene-bis-indenylzirconium dichloride (EBI). The system was stirred in N₂ atmosphere at20° C. for 1 hour. A clear solution was obtained at the end of thisperiod.

Preparation of the catalyst

A reactor with capacity of 1000 cm³, equipped with an anchor stirrer,and treated with N₂ at 90° C. for 3 hours, was loaded, at 20° C. in anitrogen atmosphere, with 600 cm³ of heptane and 60 g of the supportprepared previously. While stirring at 20° C., 238 cm³ of hexanesolution of TIBAL (100 g/l) were introduced in 30 minutes. The mixturewas heated to 80° C. in 1 hour and kept at this temperature for 2 hours.The mixture was then cooled to 20° C. and 62.5 cm³ of the TIBAL/EBIsolution previously prepared were added. The system was heated to 60° C.in 30 minutes and kept at this temperature for 2 hours. At the end ofthis period 3 washings with hexane were effected at 60° C., removing thesolvent by evaporation under vacuum at maximum temperature of about 60°C. Approximately 62 g of spherical catalyst, with the followingcharacteristics, was obtained: Mg=21.33%; Cl=66.59%; Al=0.96%; Zr=0.41%;ETO=0.3%;

Surface area (Hg) 70.9 m² /g

Porosity (Hg) 1.041 cm³ /g

Surface area (BET) 61.9 m² /g

Porosity (BET) 0.687 cm³ /g

Polymerization (LLDPE)

0.05 g of the catalyst described above and 0.42 g of methyl alumoxane(MAO) in 100 cm³ of toluene were pre-contacted for 5 minutes at 20° C.in a glass flask, which had been treated with N₂ at 90° C. for 3 hours.The whole was placed in a 4-liter steel autoclave, equipped with ananchor stirrer, and treated with N₂ at 90° C. for 3 hours, containing800 g of propane at 30° C. The autoclave was heated to 75° C. and 0.1bar of H₂ was introduced and then, simultaneously, 7 bar of ethylene and100 g of 1-butene. Polymerization was carried out for 1 hour, keepingthe temperature and the ethylene pressure constant. 115 g ofethylene-butene copolymer was obtained (g copolymer per g catalyst=2300;kg copolymer per g Zr=545) with the following characteristics: MIE=0.84;F/E=49.16; η=1.35; density=0.914; butene=10.1%; insoluble inxylene=97.42%.

Polymerization (HDPE)

0.42 g of MAO and 0.05 g of the catalyst described above in 100 cm³ oftoluene were precontacted for 5 minutes at 30° C. in a glass flask thathad been treated with N₂ at 90° C. for 3 hours. The whole was thenplaced in a 4-liter steel autoclave, equipped with an anchor stirrer andtreated with N₂ at 90° C. for 3 hours, containing 1.6 liters of hexaneat 20° C. The autoclave was heated to 75° C. and 7 bar of ethylene and0.25 bar of H₂ were introduced. Polymerization was effected for 1 hour,keeping the ethylene temperature and pressure constant. Polymerizationwas stopped by instantaneous degassing of the autoclave and, aftercooling to 20° C., the polymer slurry was discharged and was dried at80° C. in nitrogen atmosphere. 100 g of polyethylene were obtained (2000g polyethylene/g catalyst; 492 kg polyethylene/g Zr), with the followingcharacteristics: MIE=12.9; F/E=22.5; η=0.7.

EXAMPLE 2

Preparation of the metallocene/alumoxane solution

A 1000 cm³ reactor, equipped with an anchor stirrer and treated with N₂,was loaded with 600 cm³ of toluene, 18.87 g of polymethyl-alumoxane(MAO) and 8.46 g of EBI. The system was stirred in an atmosphere of N₂at 20° C. for 1 hour. A clear solution was obtained at the end of thisperiod.

Preparation of the catalyst

A 1000 cm³ reactor, equipped with an anchor stirrer and treated with N₂at 90° C. for 3 hours, was fed, in an atmosphere of N₂ at 20° C., with600 cm³ of heptane and 60 g of support prepared according to themethodology in Example 1. While stirring at 20° C., 86.4 cm³ of solutionof trimethylaluminium (TMA) in hexane (100 g/liter) were introduced in30 minutes. In 1 hour the system was heated to 80° C. and was maintainedat this temperature for 2 hours. The mixture was then Cooled to 20° C.and 62.5 cm³ of the MAO/EBI solution previously prepared wereintroduced. The system was heated to 60° C. in 30 minutes and was keptat this temperature for 2 hours. At the end of this period, 3 washingswith hexane were effected at 60° C., removing the solvent by evaporationunder vacuum at maximum temperature of about 60° C. 65 g of sphericalcatalyst with the following characteristics was obtained: Mg=19.3%;Cl=61.5%; Al=3.87%; Zr=0.33%; OEt=4.3%.

Polymerization (HDPE)

0.05 g of the catalyst described above was precontacted with MAO (0.42g) in the conditions of Example 2. Then ethylene was polymerized in theconditions in Example 2, obtaining 100 g of polymer (2000 gpolyethylene/g cat; 575 kg polymer/g Zr) with the followingcharacteristics: MIE=9.5; F/E=12.68; η=0.66.

EXAMPLE 3

Preparation of the metallocene/alumoxane solution

Preparation was effected in the same conditions as Example 2 but using47.18 g of MAO instead of 18.87 g.

Preparation of the catalyst

The catalyst was prepared following the procedure described in Example2, using 166.6 cm³ of the metallocene-alumoxane solution describedabove. Once the solvent had been removed by evaporation, approx. 65 g ofspherical catalyst with the following characteristics were obtained:Mg=18.41; Cl=57.5; Al=5.56; Zr=0.42.

Polymerization (HDPE)

0.05 g of the catalyst described above was precontacted and polymerizedin the same conditions as in Example 1, using 0.1 bar of H₂ instead of0.25 bar. 80 g of polyethylene were obtained (1600 g polyethylene/g cat;381 kg polyethylene/g Zr), with the following characteristics: MIE=5.9;F/E=17.9; η=0.77.

EXAMPLE 4

Preparation of the support

A spherical adduct MgCl₂.3EtOH was prepared following the proceduredescribed in Example 2 of Patent U.S. Pat. No. 4,399,054, operating at3000 rpm instead of at 10000 rpm. The adduct was partially dealcoholizedby heating in a stream of nitrogen at temperatures increasing from 30°C. to 180° C., until an adduct containing 35% by weight of EtOH wasobtained.

Preparation of the metallocene/triisobutylaluminium solution

A reactor with capacity of 1000 cm³, equipped with an anchor stirrer andtreated with N₂, was loaded with 382.5 cm³ of triisobutylaluminium(TIBAL) in hexane solution (100 g/liter) and 14.25 g ofethylene-bis-indenyl zirconium dichloride (EBI). The system was stirredin an atmosphere of N₂ at 20° C. for 1 hour. A clear solution wasobtained at the end of this period.

Preparation of the catalyst

A reactor with capacity of 3000 cm³, equipped with an anchor stirrer andtreated with N₂ at 90° C. for 3 hours, was loaded, at 20° C. in anatmosphere of nitrogen, with 600 cm³ of heptane and 60 g of the supportpreviously prepared. While Stirring at 20° C., 900 cm³ of hexanesolution of TIBAL (100 g/l) were introduced in 30 minutes. The mixturewas heated to 80° C. in 1 hour and was maintained at this temperaturefor 2 hours. The mixture was then cooled to 20° C. and 62.5 cm³ of theTIBAL/EBI solution prepared previously were introduced. The system washeated to 60° C. in 30 minutes and was maintained at this temperaturefor 2 hours. At the end of this period, 3 washings were effected withhexane at 60° C., removing the solvent by evaporation under vacuum atthe maximum temperature of about 60° C. After drying, about 65 g ofcatalyst with the following characteristics were obtained: Zr=0.6%;Mg=15.3%; Cl=48.2%; Al=4.6%;

Surface area (Hg) 24.1 m² /g

Porosity (Hg) 0.359 cm³ /g

Surface area (BET) 129.2 m² /g

Porosity (BET) 0.837 c³ /g

Polymerization (LLDPE)

0.05 g of the catalyst described above was precontacted and polymerizedfollowing the same procedure as in Example 1, using 0.25 bar of H₂instead of 0.1 bar. At the end, 170 g of ethylene-butene copolymer wereobtained (3400 g copolymer/g cat; 564 kg copolymer/g Zr) with thefollowing characteristics: MIE=4.76; F/E=32.2; η=1.1; density=0.9135;butene=10.5%; insoluble in xylene=95%.

EXAMPLE 5

Preparation of the catalyst

A reactor with capacity of 1000 cm³, equipped with an anchor stirrer andtreated with N₂ at 90° for 3 hours, was loaded, in an atmosphere of N₂at 20° C., with 500 cm³ of toluene and 100 g of the support preparedaccording to the procedure in Example 4. While stirring at 20° C., 55 gof trimethylaluminium (heptane solution 100 g/l) were introduced, andthen the mixture was heated at 105° C. for 3 hours. At the end thetemperature was lowered to 20° C. and 102 cm³ of the TIBAL/EBI solutionprepared according to the procedure in Example 4 were introduced, thenthe whole was heated at 80° C. for 2 hours. After removing the solventby evaporation, about 120 g of spherical catalyst with the followingcharacteristics were obtained: Zr=0.6%; Mg=16.5%; Cl=49.2%; Al=6.7%;

Surface area (Hg) 33.8 m² /g

Porosity (Hg) 0.495 cm³ /g

Surface area (BET) 171.3 m² /g

Porosity (BET) 0.291 cm³ /g

Polymerization (HDPE)

0.05 g of the catalyst described above was precontacted and polymerizedin the same conditions of Example 1, using 0.1 bar of H₂ instead of 0.25bar. 115 g of polyethylene (2300 g polyethylene/g cat) with thefollowing characteristics were obtained: MIE=0.78; F/E=66.8.

EXAMPLE 6

Preparation of the support

A spherical adduct MgCl₂.3EtOH was prepared following the proceduredescribed in Example 2 of Patent U.S. Pat. No. 4,399,054, operating at3000 rpm instead of at 10000 rpm. The adduct was partially dealcoholizedby heating in a stream of nitrogen at temperatures increasing from 30°C. to 180° C., until an adduct containing 45% by weight of EtOH wasobtained. 2360 g of spherical adduct thus obtained were loaded into a30-liter reactor containing 18 liters of hexane. While stirring at roomtemperature, 1315 g of AlEt₃ in hexane solution (100 g/liter) wereintroduced. The mixture was heated to 60° C. in 60 minutes and wasmaintained at this temperature for 60 minutes. The liquid phase wasseparated and 15 liters of hexane were introduced. The treatment withAlEt₃ was repeated twice more operating under the same conditions. Atthe end, the spherical support obtained was washed 5 times with hexaneand was dried under vacuum.

Preparation of the catalyst

A 1000 cm³ reactor, equipped with an anchor stirrer and treated with N₂at 90° C. for 3 hours, was loaded, in an atmosphere of nitrogen at 20°,with 500 cm³ of toluene and 60 g of support. 53.68 cm³ of themetallocene/TIBAL solution prepared according to the procedure inExample 4 were then introduced, stirring continuously for 2 hours at 20°C. At the end, four washings were effected with hexane at 20° C.,removing the solvent by evaporation under vacuum. About 62 g ofspherical catalyst with the following characteristics were obtained:Zr=1.1%; Mg=16.6%; Cl=55.3%; Al=3.6%; OEt=3.2%;

Surface area (Hg) 38.3 m² /g

Porosity (Hg) 0.604 cm³ /g

Surface area (BET) 298.9 m² /g

Porosity (BET) 0.327 cm³ /g

Polymerization (LLDPE)

0.05 g of the catalyst described above was polymerized using the sameprocedure as in Example 1, obtaining 160 g of ethylene-butene copolymer(3200 g copolymer/g cat; 290 kg copolymer/g Zr) with the followingcharacteristics: MIE=1.28; F/E=50.7; butene=10.5%; η=1.37; insoluble inxylene=95.32%; density=0.9122.

The test was repeated using 1.45 g of TIBAL instead of 0.42 g of MAO and1 bar of H₂ instead of 0.1. 10 g of copolymer was obtained (200 gcopolymer/g cat; 17.3 kg copolymer/g Zr) with η=0.3.

EXAMPLE 7

Preparation of the catalyst

The catalyst was prepared according to the procedure of Example 6,except that the four washings with hexane were not effected at the endof the preparation. About 63 g of spherical catalyst were obtained, withthe following characteristics: Zr=1.11%; Mg=13%; Cl=44.8%; Al=3.9%;

OEt=6.4%;

Surface area (Hg) 19.7 m² /g

Porosity (Hg) 0.476 c³ /g

Surface area (BET) 230.2 m² /g

Porosity (BET) 0.197 cm³ /g

Polymerization (LLDPE)

0.05 g of the catalyst described above was polymerized according to themethodology described in Example 1, using 1 bar of H₂ instead of 0.1 and150 g of butane instead of 100. 330 g of ethylene-butane copolymer wereobtained (6600 g copolymer/g cat; 597 kg copolymer/g Zr), with thefollowing characteristics: MIE=16.3; F/E=34.6; η=0.76; density=0.9097;Mw/Mn=3.7.

EXAMPLE 8

Preparation of the catalyst

A reactor with capacity of 1000 cm³, equipped with an anchor stirrer andtreated with N₂ at 90° C. for 3 hours, was loaded, in an atmosphere ofN₂ at 20° C., with 600 cm³ of heptane and 60 g of support preparedaccording to the methods in Example 6. While stirring at 20° C., 86.4cm³ of solution of trimethyl-aluminium (TMA) in hexane (100 g/liter)were introduced in 30 minutes. The system was heated to 80° C. in 1 hourand was maintained at this temperature for 2 hours. The solution wasthan cooled to 20° C. and 272 cm³ of EBI/MAO solution prepared accordingto the procedure of Example 3 were introduced. The mixture was heated to60° C. in 30 minutes and was maintained at this temperature for 2 hours.At the end of this period the solvent was removed by evaporation undervacuum at maximum temperature of about 60° C. for about 3 hours. About63 g of spherical catalyst with the following characteristics wereobtained: Zr=0.8%; Mg=12.6%; Cl=40%; Al=9.3%.

Polymerization (LLDPE)

0.05 g of the catalyst described above was used for the preparation ofan ethylene-butene copolymer according to the procedure in Example 1,using 1.45 g of TIBAL instead of 0.42 g of MAO. At the end, 45 g ofcopolymer were obtained (900 g copolymer/g cat; 110 kg copolymer/g Zr),with the following characteristics: MIE=8.34; F/E=28.91; η=1.15;insoluble in xylene=81.5%; density=0.905.

EXAMPLE 9

Preparation of support

The support was prepared according to the procedure described in Example1.

Preparation of the catalyst

In a 1000 cm³ reactor, equipped with a mechanical stirrer and pretreatedwith N₂ at 90° C. for 3 hours, 600 cm³ of hexane and 120 g of the abovedescribed support were fed at 20° C. under a nitrogen atmosphere; 16.2 gof isoamyl ether was then added over 30 minutes and the system washeated to 50° C. and kept at this temperature for 1 hour. At the end ofthis period it was cooled to 20° C., 5 g of ethylene bisindenylzirconium chloride was added and the whole was kept stirred for 15minutes. Then, 15.7 g of diethyl aluminium monochloride (100 g/lsolution in hexane) was added and the mixture was heated to 40° C.maintaining at this temperature for 1 hour. After this period, themixture was cooled to 20° C., the solid was allowed to settle and theliquid phase was removed. 600 cm³ of hexane and 15.7 g of AlEt₂ Cl werefed and the above described treatment was repeated. Finally the productwas washed three times with 200 cm³ of hexane at 60° and three timeswith 200 cm³ of hexane at 20°, obtaining 102 g of spherical catalystcomponent having the following characteristics: Mg=21.4%; Cl=65.79%;Al=0.3%; Zr=0.67%; isoamyl ether=2.0%; ETO=3.8%.

Polymerization (HDPE)

The so obtained catalyst was used to prepare HDPE according to theprocess described in Example 2. 240 g of polymer were obtained (4813 gPE/g catalyst; 780 Kg PE/g Zr) having the following characteristics:MIE=1.02; F/E=62; η=1.08; Mw/Mn=2.9.

EXAMPLE 10

Preparation of support

The support was prepared according to the procedure described in Example6.

Preparation of the metallocene/triisobutylaluminium solution

In a 1000 cm³ reactor, equipped with mechanical stirrer and purged withnitrogen, 620 cm³ of triisobutyl aluminium in hexane solution. (100 g/l)and 42 g of ethylene-bis-4,7-dimethylindenyl zirconium dichloride(EBDMI) were fed. The reaction was carried out as described in Example1.

Preparation of the catalyst

Into a previously purged 2 l reactor, 250 cm³ of heptane and 35 g of theabove described support were fed. The mixture was cooled to 0° C. and505 cm³ of TIBAL (100 g/l solution in hexane) were added; the whole washeated to 60° C. for 1 hour and subsequently cooled to 20° C. 31 cm³ ofthe above described EBDMI/TIBAL solution was fed and the mixture washeated to 70° C. for 2 hours, after which it was cooled to 20° C.; thesolid was allowed to settle and the liquid was siphoned. After dryingunder vacuum at 50° C., about 30 g of spherical catalyst was obtained,having the following characteristics: Mg=15.95%; Cl=54.75%; Al=3.2%;Zr=0.98%; EtO=7.0%.

Polymerization (LLDPE)

The so obtained catalyst was used in the preparation of LLDPE accordingto example 1, using 1.45 g of TIBAL instead of 0.42 g of MAO. 100 g ofcopolymer was obtained (g copolymer/g cat=2000; Kg of copolymer/gZr=200) having the following characteristics: MIE=0.48; F/E=45.83;density=0.919; Insolubility in xylene=98.51%.

EXAMPLE 11

Preparation of support

The support was prepared according to the procedure described in Example8.

Preparation of the metallocene/methylaluminoxane solution

Into a previously purged one liter reactor, 600 cm³ of toluene, 76.5 gof methylaluminoxane and 15.6 g of EBDMI were fed; the system was keptunder stirring at 20° C. for 2 hours.

Preparation of the catalyst

Into a previously purged 1 liter reactor, 200 cm³ of toluene and 100 gof the above described support were added; subsequently 200 cm³ of theabove described metallocene/MAO solution was added and the system washeated to 40° C. and kept stirred at this temperature for 2 hours.Finally the solid was allowed to settle and the liquid was removed bysyphoning. The obtained sold was then washed four times with 200 cm³ ofhexane at 20° C. and subsequently dried. 125 g of spherical catalyst wasobtained having the following characteristics: Cl=45.35%; Mg=16.25%;Al=7.1%; Zr=0.45%.

Polymerization (LLDPE)

The above described catalyst was used to prepare LLDPE according to theprocedure of example 10. 37.7 g of polymer were obtained (754 gcopolymer/g catalyst; 167 Kg of copolymer/g di Zr) with the followingcharacteristics: MIE=0.4; F/E=46.25; Insolubility in xylene=97%; η=1.77;Density=0.913.

We claim:
 1. A component of catalysts for the polymerization of olefinscomprising a compound of a transition metal M selected among Ti, V, Zrand Hf containing at least one M-π bond, and a halide of Mg,characterized by surface area (BET) greater than about 50 m² /g,porosity (BET) greater than 0.15 cm³ /g and porosity (Hg) greater than0.3 cm³ /g, with the proviso that when the surface area is less thanabout 150 m² /g, the porosity (Hg) is less than about 1.5 cm³ /g.
 2. Acomponent according to claim 1, having surface area greater than 150 m²/g and porosity (BET) greater than 0.2 cm³ /g.
 3. A component accordingto claim 1, having surface area less than 150 m² /g and porosity (Hg)between 0.5 and 1.2 cm³ /g.
 4. A component according to claim 1, whereinmore than 40% of the porosity (BET) is due to pores with radius greaterthan 300 Å.
 5. A component according to claim 1, wherein more than 50%of the porosity (BET) is due to pores with radius between 600 Å and 1000Å.
 6. A component according to claim 1 in the form of spheroidalparticles with size smaller than 150 microns.
 7. A component accordingto claim 1 obtained by supporting a compound of a transition metal Mselected from Ti, V, Zr and Hf containing at least one M-π bond, on ahalide of Mg or on a support containing a halide of Mg that has surfacearea between 200 and 800 m² /g and porosity (BET) greater than 0.3 cm³/g and porosity (Hg) greater than 0.3 cm³ /g.
 8. A component accordingto claim 7, wherein the halide of Mg is in the form of spheroidalparticles with size smaller than 150 microns.
 9. A component accordingto claim 7, wherein the halide of Mg is supported on an inert supportselected from silica, alumina, silica-alumina possessing surface areabetween 300 and 600 m² /g and porosity (BET) greater than 0.5 c³ /g andpartially crosslinked polystyrene with surface area between 100 and 500m² /g and porosity (BET) greater than 0.5 c³ /g.
 10. A componentaccording to claim 8, wherein the halide of Mg is obtained fromspherulized MgX₂, alcohol adducts that are then reacted with an alkyl-Alcompound to remove the alcohol.
 11. A component according to claim 10,wherein the Mg halide is Mg chloride obtained from MgCl₂.3ROH adducts,in which R is an alkyl radical with 1-8 carbon atoms, which aresubmitted to partial dealcoholizing and then reacted with the alkyl-Alcompound.
 12. A component according to claim 1, wherein the transitionmetal compound contains at least one ligand L coordinated on the metalM, which has a mono- or polycyclic structure containing conjugated πelectrons.
 13. A component according to claim 12, wherein the transitionmetal compound is selected from compounds having the structure:

    Cp.sup.I MR.sub.a.sup.1 R.sub.b.sup.2 R.sub.c.sub.3        (I)

    Cp.sup.I 1Cp.sup.II MR.sub.a.sup.1 R.sub.b.sup.2           (II)

    (Cp.sup.I -A.sub.e -Cp.sup.II)MR.sub.a.sup.1 R.sub.b.sup.2 (III)

in which M is Ti, V, Zr or Hf; CpI and Cp^(II), identical or different,are cyclopentadienyl groups, including substituted ones; two or moresubstituents on the said cyclopentadienyl groups can form one or morerings possessing from 4 to 6 carbon atoms; R¹, R² and R³, identical ordifferent, are atoms of hydrogen, halogen, an alkyl or alkoxyl groupwith 1-20 carbon atoms, aryl, alkaryl or aralkyl with 6-20 carbon atoms,an acyloxy group with 1-20 carbon atoms, an allyl group, a substituentcontaining a silicon atom; A is an alkenyl bridge or one with structureselected from: ##STR2## ═BR₁, ═AlR₁, --Ge--, --Sn--, --O--, --S--, ═SO,═SO₂, ═NR₁, ═PR₁, ═P(O)R₁, in which M₁ is Si, Ge, or Sn; R₁ and R₂,identical or different, are alkyl groups with 1-4 carbon atoms or arylgroups with 6-10 carbon atoms; a, b, c are, independently, integers from0 to 4; e is an integer from 0 to 6 and two or more of the radicals R¹,R² and R³ can form a ring.
 14. A component according to claim 12,wherein the transition metal compound is selected from compounds thathave the structure: (Me₅ Cp)MMe₃, (Me₅ Cp)M(OMe)₃, (Me₅ Cp)MCl₃,(Cp)MCl₃, (Cp)MMe₃, (MeCp)MMe₃, (Me₃ Cp)MMe₃, (Me₄ Cp)MCl₃, (Ind)MBenz₃,(H₄ Ind)MBenz₃, and (Cp)MBu₃.
 15. A component according to claim 12,wherein the transition metal compound is selected from compounds thathave the structure: (Cp)₂ MMe₂, (Cp)₂ MPh₂, (Cp)₂ MEt₂, (Cp)₂ MCl₂,(Cp)₂ M(OMe)₂, (Cp)₂ M(OMe)Cl, (MeCp)₂ MCl₂, (Me₅ Cp)₂ MCl₂, (Me₅ Cp)₂MMe₂, (Me₅ Cp)₂ MMeCl, (Cp)(Me₅ Cp)MCl₂, (1-MeFlu)₂ MCl₂, (BuCp)₂ MCl₂,(Me₃ Cp)₂ MCl₂, (Me₄ Cp)₂ MCl₂, (Me₅ Cp)₂ M(OMe)₂, (Me₅ Cp)₂ M(C₆ H₅)₂,(Me₅ Cp)₂ M(CH₃)Cl, (EtMe₄ Cp)₂ MCl₂, (C₆ H₅)Me₄ Cp!₂ MCl₂, (Et₅ Cp)₂MCl₂, (Me₅ Cp)₂ M(C₆ H₅)Cl, (Ind)₂ MCl₂, (Ind)₂ MMe₂, (H₄ Ind)₂ MCl₂,(H₄ Ind)₂ MMe₂, { Si(CH₃)₃ !Cp}₂ MCl₂, { Si(CH₃)₃ !₂ Cp}₂ MCl₂, and (Me₄Cp)(Me₅ Cp)MCl₂.
 16. A component according to claim 12, wherein thetransition metal compound is selected from compounds that have thestructure: C₂ H₄ (Ind)₂ MCl₂, C₂ H₄ (Ind)₂ MMe₂, C₂ H₄ (H₄ Ind)₂ MCl₂,C₂ H₄ (H₄ Ind)₂ MMe₂, Me₂ Si(Me₄ Cp)₂ MCl₂, Me₂ Si(Me₄ Cp)₂ MMe₂, Me₂SiCp₂ MCl₂, Me₂ SiCp₂ MMe₂, Me₂ Si(Me₄ Cp)₂ MMeOMe, Me₂ Si(Flu)₂ MCl₂,Me₂ Si(2-Et-5-iPrCp)₂ MCl₂, Me₂ Si(H₄ Ind)₂ MCl₂, Me₂ Si(H₄ Flu)₂ MCl₂,Me₂ SiCH₂ (Ind)₂ MCl₂, Me₂ Si(2-Me-H₄ Ind)₂ MCl₂, Me₂ Si(2-MeInd)₂ MCl₂,Me₂ Si(2-Et-5-iPr-Cp)₂ MCl₂, Me₂ Si(2-Me-5-EtCp)₂ MCl₂, Me₂Si(2-Me-5-Me-Cp)₂ MCl₂, Me₂ Si(2Me-4,5-benzoindenyl)₂ MCl₂, Me₂Si(4,5-benzoindenyl)₂ MCl₂, Me₂ Si(2-EtInd)₂ MCl₂, Me₂ Si(2-iPr-Ind)₂MCl₂, Me₂ Si(2-t-butyl-Ind)MCl₂, Me₂ Si(3-t-butyl-5-MeCp)₂ MCl₂, Me₂Si(3-t-butyl-5-MeCp)₂ MMe₂, Me₂ Si(2-MeInd)₂ MCl₂, C₂ H₄(2-Me-4,5-benzoindenyl)₂ MCl₂, Me₂ C(Flu)CpMCl₂, Ph₂ Si(Ind)₂ MCl₂,Ph(Me)Si(Ind)₂ MCl₂, C₂ H₄ (H₄ Ind)M(NMe₂)OMe,isopropylidene-(3-t-butyl-Cp)(Flu)MCl₂, Me₂ C(Me₄ Cp)(MeCp)MCl₂,MeSi(Ind)₂ MCl₂, Me₂ Si(Ind)₂ MMe₂, Me₂ Si(Me₄ Cp)₂ MCl(OEt), C₂ H₄(Ind)₂ M(NMe₂)₂, C₂ H₄ (Me₄ Cp)₂ MCl₂, C₂ Me₄ (Ind)₂ MCl₂, Me₂ Si(3-Me-Ind)₂ MCl₂, C₂ H₄ (2-Me-Ind)₂ MCl₂, C₂ H₄ (3-Me-Ind)₂ MCl₂, C₂ H₄(4,7-Me₂ -Ind)₂ MCl₂, C₂ H₄ (5,6-Me₂ -Ind)₂ MCl₂, C₂ H₄ (2,4,7-Me₃ Ind)₂MCl₂, C₂ H₄ (3,4,7-Me₃ Ind)₂ MCl₂, C₂ H₄ (2-Me-H₄ Ind)₂ MCl₂, C₂ H₄(4,7-Me₂ -H₄ Ind)₂ MCl₂, C₂ H₄ (2,4,7-Me₃ -H₄ Ind)₂ MCl₂, Me₂ Si(4,7-Me₂-Ind)₂ MCl₂, Me₂ Si(5,6-Me₂ -Ind)₂ MCl₂, and Me₂ Si(2,4,7-Me₃ -H₄ Ind)₂MCl₂.
 17. A component according to claim 1, wherein the transition metalcompound is present in a quantity of from 0.1 to 5% by weight expressedas metal.
 18. A catalyst for the polmerization of olefins comprising theproduct of the reaction of a component according to claim 1 with analkyl-Al compound selected from trialkyl-Al's in which the alkyl groupshave from 1 to 12 carbon atoms and linear or cyclic alumoxane compoundscontaining the repeating unit -(R₄)AlO--, in which R₄ is an alkyl groupwith 1-6 carbon atoms or a cycloalkyl or aryl group with 6-10 carbonatoms and containing from 2 to 50 repeating units.
 19. A catalystaccording to claim 18, wherein the alkyl-Al compound is a mixture oftrialkyl-Al and an alumoxane.
 20. A catalyst according to claim 18,wherein the alumoxane is polymethyl-alumoxane.
 21. A catalyst accordingto claim 18, wherein the trialkyl-Al compound is reacted with 0.5-0.01mol of water per mole of trialkyl-Al and in which the compound oftransition metal M is selected from: C₂ H₄ (Ind)₂ MCl₂, C₂ H₄ (Ind)₂MMe₂, C₂ H₄ (H₄ Ind)₂ MCl₂, C₂ H₄ (H₄ Ind)₂ MMe₂, Me₂ Si(Me₄ Cp)₂ MCl₂,Me₂ Si(Me₄ Cp)₂ MMe₂, Me₂ SiCp₂ MCl₂, Me₂ SiCp₂ MMe₂, Me₂ Si(Me₄ Cp)₂MMeOMe, Me₂ Si(Flu)₂ MCl₂, Me₂ Si(2-Et-5-iPrCp)₂ MCl₂, Me₂ Si(H₄ Ind)₂MCl₂, Me₂ Si(H₄ Flu)₂ MCl₂, Me₂ SiCH₂ (Ind)₂ MCl₂, Me₂ Si(2-Me-H₄ Ind)₂MCl₂, Me₂ Si(2-MeInd)₂ MCl₂, Me₂ Si(2-Et-5-iPr-Cp)₂ MCl₂, Me₂Si(2-Me-5-EtCp)₂ MCl₂, Me₂ Si(2-Me-5-Me-Cp)₂ MCl₂, Me₂Si(2Me-4,5-benzoindenyl)₂ MCl₂, Me₂ Si(4,5-benzoindenyl)₂ MCl₂, Me₂Si(2-EtInd)₂ MCl₂, Me₂ Si(2-iPr-Ind)₂ MCl₂, Me₂ Si(2-t-butyl-Ind)MCl₂,Me₂ Si(3-t-butyl-5-MeCp)₂ MCl₂, Me₂ Si(3-t-butyl-5-MeCp)₂ MMe₂, Me₂Si(2-MeInd)₂ MCl₂, C₂ H₄ (2-Me-4,5-benzoindenyl)₂ MCl₂, Me₂C(Flu)CpMCl₂, Ph₂ Si(Ind)₂ MCl₂, Ph(Me)Si(Ind)₂ MCl₂, C₂ H₄ (H₄Ind)M(NMe₂)OMe, isopropylidene-(3-t-butyl-Cp)(Flu)MCl₂, Me₂ C(Me₄Cp)(MeCp)MCl₂, MeSi(Ind)₂ MCl₂, Me₂ Si(Ind)₂ MMe₂, Me₂ Si(Me₄ Cp)₂MCl(OEt), C₂ H₄ (Ind)₂ M(NMe₂)₂, C₂ H₄ (Me₄ Cp)₂ MCl₂, C₂ Me₄ (Ind)₂MCl₂, Me₂ Si(3 -Me-Ind)₂ MCl₂, C₂ H₄ (2-Me-Ind)₂ MCl₂, C₂ H₄ (3-Me-Ind)₂MCl₂, C₂ H₄ (4,7-Me₂ -Ind)₂ MCl₂, C₂ H₄ (5,6-Me₂ -Ind)₂ MCl₂, C₂ H₄(2,4,7-Me₃ Ind)₂ MCl₂, C₂ H₄ (3,4,7-Me₃ Ind)₂ MCl₂, C₂ H₄ (2-Me-H₄ Ind)₂MCl₂, C₂ H₄ (4,7-Me₂ -H₄ Ind)₂ MCl₂, C₂ H₄ (2,4,7-Me₃ -H₄ Ind)₂ MCl₂,Me₂ Si(4,7-Me₂ -Ind)₂ MCl₂, Me₂ Si(5,6-Me₂ -Ind)₂ MCl₂, and Me₂Si(2,4,7-Me₃ -H₄ Ind)₂ MCl₂.
 22. A component according to claim 12,wherein the transition metal compound is selected from the groupconsisting of (Me₅ Cp)₂ M(OH)Cl and (Me₅ Cp)₂ M(OH)₂.